Conventionally, endoscopes have been used in the medical and other fields for the purpose of examinations and treatments. An endoscope 200 of this type includes, as depicted in FIG. 6, a main body part 201 and a flexible tube 203 to be joined to the main body part 201 and inserted inside the body of a person to be operated and having a curved part 202 at the tip. The main body part 201 is provided with an operating part 204 capable of curving the curved part 202 provided at the tip of the flexible tube 203 as appropriate.
Inside the flexible tube 203, an operation wire (not shown) is arranged, having a tip fixed to the curved part 202 for curving the curved part 202 by pulling. By driving and pulling this operation wire by appropriate means, the curved part 202 is curved in upper, lower, left, and right directions for examination, treatment, and others. The main body part 201 is provided with an operating part 204. In the case of a manual operation by an operator, a wire pulling operation is generally performed by a rotary dial 205.
Inside the flexible tube 203, a forceps channel 206 through which any of various treatment tools is inserted is provided. When a region required to be examined is found in an internal organ at the time of examination, for example, a metal ring called a snare is hooked in the region required to be examination and, for example, a high-frequency current is caused to flow through to cut the region (endoscopic mucosal resection) or a large lesion is cut out by a dedicated treatment tool (endoscopic submucosal dissection), thereby checking the state of a tissue with a microscope.
Therefore, in the main body part 201 of the endoscope, a treatment tool insertion part 207 is provided so as to allow various treatment tools to be inserted from outside through the forceps channel 206 to project from the tip of the curved part 202 to the inside of the internal organ.
In this case, since a portion required to be examined is extracted or blood is suctioned by various treatment tools through the treatment tool insertion part 207, the inside of the treatment tool insertion part is required to be clean and, when used in an examination, is always subjected to sterilization and disinfection by means of sterilization with EOG (ethylene oxide gas), sterilization with gamma rays, sterilization by boiled water, and others. Also, if frequently used with a treatment tool or the like inserted thereinto, the treatment tool insertion part may be broken, possibly leading to replacement as required. Therefore, the treatment tool insertion part is desired to allow easy sterilization and disinfection and to be easily removed.
However, the treatment tool insertion part 207 itself of the conventional endoscope is not configured to be removable from the main body part 201 (Patent Document 1).
Moreover, it has been conventionally suggested that a treatment tool insertion part is configured in an operating part of an endoscope with a base end part projecting outward and integrally provided and a tip part removably jointed to the base end part (Patent Document 2).
However, in the technology described in Patent Document 2, while the tip part can be removed, the base end part forming the treatment tool insertion part is integrally provided to an operating part of the endoscope, and therefore an inconvenience still exists such that cleaning and disinfection and sterilization of a treatment tool insertion tube inside may not be able to be easily performed at the time of clearing and disinfection and sterilization
Moreover, since the treatment tool insertion part has various insertion tools inserted therein and removed therefrom, the treatment tool insertion part may be broken and be required to be replaced. However, the conventional treatment tool insertion part is configured of the base end part and the tip part, has a complex structure, and has a possibility of being easily broken, and even in the case of component replacement, there is a possibility of increasing component cost.    [Patent Document 1] Japanese Utility Model Publication No. 1-11201    [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2005-185636